Okay... he doesn't sound as if he needs any salts. Those aren't signs of parasites (either internal or external), nor SBD.

Sounds more like he is comfortable in his home, he is finding new places to sleep, he is being lazy about getting some air.. tilting while sleeping is normal.. there is no certain speed they swim at constantly. SBD he will have trouble keeping upright at all times, swimming either up or down (not speed, but literally thrashing and working hard to swim).

If he is eating just fine (2-3 pellets per meal 2x a day).. then leave him be and continue to watch him. But honestly, with what you are describing, it doesn't sound like he is ill... just being a fish. I can't count how many times my fish change any pattern they set when it comes to sleeping.. just this morning my oldest one was head down into the gravel leaning against his cave when he is usually in his plant or in his cave in the mornings. So they do change their routine as they go.. he just happened to of fell asleep there when he got tired.

The last line of the original post states white stringy poo which is typically an indication of internal a parasites, right?